I have a single 4.16kV 600A feed that powers two 600 amp substations. From substation 1 I have a dedicated 300A/4.16kV circuit that feeds a 700A bus bar section. From substation 2 I have another dedicated 300A/4.16kV circuit that feeds another 700A bus bar section. Can I physically jumper the two bus bar sections together while keeping the two 300A circuits energized so I now have a single bus bar capable of 600A as opposed to two independent 300A bus bars.
Parallel HV
- Thread starter tlona1
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Can you. Yes if proper safety procedures allow it. Why would you want to?
1. You need to verify that the phasing is correct with a meter.
2. Your fault current will be twice what it was.
3. Fault on one transformer may take both out of service.
4. Why not use a tie breaker with a normal open position.
1. You need to verify that the phasing is correct with a meter.
2. Your fault current will be twice what it was.
3. Fault on one transformer may take both out of service.
4. Why not use a tie breaker with a normal open position.
- Location
- Lockport, IL
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- Retired Electrical Engineer
Without seeing the entire one-line diagram, I cannot be certain. But it sounds as though you might be putting the two 300 amp overcurrent devices in parallel. That would not be allowed.
it is for a marine crane operation. The clients operation now calls for the addition of a third crane which is 200A (the existing two are 150A each) so one bus section cannot handle two cranes and also all three need to be able to run the full length of the warf which is about 800ft. In our case the two feeders would essentially now be considered a parallel feeder to the bus with independent feeder protection. So i though not only I would have phasing issues because of the log distance between the feeders, but also would not comply with NEC 240.8 for parallel feeder protection.
300+300=300
300+300=300
Connecting the two busses together makes a longer 300 amp bus not a 600 amp bus.
Medium voltage equipment is usually has fault capacity rated in MVA not amps.
Paralleling the 300 amp buses could have increased the fault current. I would check it.
300+300=300
Connecting the two busses together makes a longer 300 amp bus not a 600 amp bus.
Medium voltage equipment is usually has fault capacity rated in MVA not amps.
Paralleling the 300 amp buses could have increased the fault current. I would check it.
IslandSparky
Member
Are the cranes ultimately AC or DC? If DC, you might be able to do two rectifiers in parallel with blocking diodes and interlock the inputs. If AC, you would need supplemental relaying and confirmation that the two sources can be tied. As others stated, that is a difficult assumption to make.
Thank-you all. This is a great forum!! You have confirmed what I suspected. Each bus is rated for 700A. So now we will persue the path of increasing the two 300A feeders to 600A since my substations are 600A rated. i can then install a small bus section (about 50ft) with feeder and isolators that will allow the cranes to move between the two existing sections. It is all do-able but just like anything else, time and money!! the cranes are mostly DC and any rectifier mods would have to come from the manufacturer which really is not an option for us. Thank-you all again for your worldly input
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